Re: [PATCH v4 17/40] KVM: arm64: Move userspace system registers into separate function

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Hi Christoffer,

On 15/02/18 21:03, Christoffer Dall wrote:
There's a semantic difference between the EL1 registers that control
operation of a kernel running in EL1 and EL1 registers that only control
userspace execution in EL0.  Since we can defer saving/restoring the
latter, move them into their own function.

ACTLR_EL1 is not used by a VHE host, so we can move this register into
the EL1 state which is not saved/restored for a VHE host.

Looking at D10.2.1 (ARM DDI 0487C.a), the statement regarding the use of ACTLR_EL1 seems to be less strong than what you state here. It looks like it would be possible to have hardware where ACTLR_EL1 would still have an effect on host EL0. I also read the comments on the version 2 of this patch but I wasn't able to find what I missing.

Cheers,

--
Julien Grall
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